Study On Preparation Of CdS Nanostructures

Cadmium sulfide(CdS)is a classicalâ…¡-â…¥semiconductor materials with a direct band gap of 2.42eV at room temperature,and shows potential applications in solar cells,optoelectronic displays and nonlinear optical devices. The nanostructures of CdS have attracted a wide range of research interests because they exhibit unique optical and electronic properties different from the bulk state of the material.These properties closely depend on the size and morphology so that it is essential to investigate the synthesis of CdS nanomaterials with diverse shapes and sizes.In this work,various liquid-phase synthesis methods are adopted to synthesize several CdS nanostructures with different morphologies.In addition,CdS/carbon nanotubes composites are fabricated by a simple wetting chemical method.1.One-dimensional CdS nanorods have been successfully prepared by chemical reaction of cadmium acetate and thiourea solution with the assistance of diethylenetriamine.The as-obtained nanorods can be indexed as the hexagonal wurtzite structure.They are with diameters of 4～12nm and lengths of above 35nm.The roles of experimental parameters such as cadmium source, organic amine and reaction temperature are also discussed,which can influence the size and morphology of CdS nanostructures.During the process of researching the formation mechanism of CdS nanorods,it is found that CdS nanofilms were initially obtained.After rolling and optimizing of structure, theses nanolamellae convert into CdS nanorods.DETA coordinates with Cd²⁺, which is critical for the formation of lamella.Furthermore,through controlling the effective concentration of reactant ions,DETA can induce equilibrium growth of CdS crystals,which is in favor of formation of 1D structure.2.CdS hollow nanospheres have been synthesized via solvothermal route from cadmium nitrate and thiourea with methanol as medium.Morphology and structures of the as-obtained products were characterized by TEM,EDS and XRD.The results show that the products are mainly onion-like CdS hollow nanospheres with hexagonal wurtzite structure.The hollow nanospheres have an external diameter of 5～17nm,hollow inner size of 3～14nm and shell thicknenss of less than 2.5nm.The function of alcohol solvent on the growth of CdS nanostructure was also studied preliminary.As absolute ethanol or 1-pentanol was employed as a substitute for solvent,the products were congeries of CdS nanoparticles and microspheres assembled by CdS nanoparticles,respectively. The results demonstrate that methanol plays a significant role in the formation of hollow structure.The formation of hollow nanospheres may be caused by curling of CdS nanoflakes under the high vapor pressure of methanol.3.Through liquid reflux route in aqueous solution and control of the feeding rate of reactant,decoration of CdS nanoparticles on the surface of multi-walled carbon nanotubes are realized via one-step route.MWCNTs interlace to form network-like frame,and numerous CdS nanoparticles cover the surface of MWCNTs or fill the space of network to structure membrane composites.CdS nanoparticles have the uniform size of about 5nm.Acid treatment enhance the activity of MWCNTs.Oxygen-containing functional groups introduced into MWCNTs are of benefit to chemical adsorption of Cd²⁺ for the reason the surface of MWCNTs can effectively fix CdS nanoparticles. Adding an appropriate amount of MWCNTs can restrict the growth of nanoparticles and prevent the congregation of particles.